886 research outputs found
Particle-hole condensates of higher angular momentum in hexagonal systems
Hexagonal lattice systems (e.g. triangular, honeycomb, kagome) possess a
multidimensional irreducible representation corresponding to and
symmetry. Consequently, various unconventional phases that combine
these -wave representations can occur, and in so doing may break
time-reversal and spin rotation symmetries. We show that hexagonal lattice
systems with extended repulsive interactions can exhibit instabilities in the
particle-hole channel to phases with either or
symmetry. When lattice translational symmetry is preserved, the phase
corresponds to nematic order in the spin-channel with broken time-reversal
symmetry, known as the phase. On the other hand, lattice translation
symmetry can be broken, resulting in various density wave
orders. In the weak-coupling limit, when the Fermi surface lies close to a van
Hove singularity, instabilities of both types are obtained in a controlled
fashion.Comment: 6 pages, 3 figures. Journal reference adde
Deleterious satellite charging and possible mitigation schemes
Electrostatic charge dissipation is one of the major concerns for satellites
operating in the Earth's orbits. Under energetic plasma conditions, they may
acquire very high negative potential (up to 10's of kV) due to the collection
of energetic plasma constituents - resulting in temporary outages and permanent
damages to onboard equipment. This study proposes and discusses a couple of
physics-based schemes capable of mitigating/ minimizing the excessive charging
effects over satellites under extreme plasma conditions in LEO/ GEO. An
estimate of charge build-up on the space objects based on the charging dynamics
as a function of ambient plasma parameters has been made. Our calculations
illustrate that in the absence of a significant charge dissipation mechanism, a
severe charging (10's kV) in the dark/ shadowed at GEO and high latitude LEO
regions. We propose that installing a suitable UV lamp and
micro/nano-structuring of the surface fabric can induce an efficient
dissipation mechanism and effectively prevent the surface from deleterious
charging effects during satellite operation. We demonstrate that the UV
illumination may maintain the satellite surface at quite a small positive
potential (~ 2 V) while the surface nanofabrication sustains it at a
sufficiently low negative potential (~ 10 V). Both concepts are shown to work
efficiently in mitigating the potential threat of massive charging and safely
performing the satellite operation.Comment: 22 pages, 9 figure
- …